While the buildings in the Malden Mills complex were old, the processes and equipment
inside were modern and involved advanced manufacturing technologies. These
processes also introduced new materials and new challenges related to the operation and protection
of the facility. Because the processes were sensitive to temperature, humidity and
other environmental conditions, many of the windows openings had been covered with plywood
in an effort to better control the climate inside the buildings. The buildings were heavily
loaded with materials that were used or produced, including tons of synthetic fabrics,
drums of adhesives and several hazardous chemicals that were used to treat the materials.
There were three manufacturing “flock” lines in the middle section of the
Monomac Building, two on the first floor and one on the second floor, making a popular
insulating fabric known as Polartec. This product consists of a base fabric upon which treated nylon fibers are affixed, standing on end, to make a type of pile fabric.
This material was produced in large quantities to meet the demand for lightweight
winter clothing.
Two flock lines were in operation on the evening the incident occurred. The production
lines were designed to operate as a continuous process. A stream of base fabric
came off a roll and received a coating of a latex based adhesive, then moved into the 60
ft. long hopper room where the nylon fibers were applied, then entered a 100 ft. long
dryer where the adhesive was set.
In the hopper room the short nylon fibers were applied to the fabric, floating
down onto the adhesive as the fabric moved under a high voltage (up to 50 kV) electrical
grid. The fibers were chemically treated to give them an inherent electrical affinity
and, as they approached base fabric, the electric field would orient the fibers, causing
them to land with only one end touching the adhesive. Different chemical treatments
were used, depending on the specific type of material that was being produced.
Although cleaning was an ongoing operation, the atmosphere in the area of the flock
lines was dusty, because of the tiny fibers, and employees working in the area were provided
with dust masks.
The dryers had to be precisely controlled to maintain the desired temperature of
450 degrees F for the proper time to set the adhesive. The fabric ran over a series of
rollers weaving through a system of heated pipes, while a special heat transfer fluid was
circulated through the pipes. Three large natural gas-fired heaters were used to heat the
fluid, one connected to each dryer. The temperature of the fluid was monitored manually
and only designated employees were authorized to adjust the settings on the heaters,
which were located in a boiler room that had been added to the west side of the building.
The heat transfer fluid utilized in the process had been identified in an insurance
industry report as a factor in 49 fires and 5 explosions over a previous ten year period.
However, mill management was unaware of the potential threat posed by the use of the
heat transfer fluid. The fluid, in the free burning state, produces a heavy black carbonaceous
cloud of smoke that is prone to ignite, allowing the fire to spread rapidly.
The tiny nylon fibers were occasionally ignited as they passed through the electrical
grid. Three different means were provided to shut down the power grid, stop the production
line and initiate a steam flood to suppress a potential explosion within the
machinery. A system of light weight nylon line was used as the first line fire detector - if
a small fire or “sparkler” developed within the electric grid this line would melt very
quickly and initiate the automatic response. An ultraviolet detection system was installed
as a second means of activation and employees could also press a manual emergency button
to achieve the same results. These systems were tested monthly, however activation
of the steam flood system did not transmit an alarm to the fire department.
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